I did it in the winter, which might explain why it didn’t work? I did it outside hidden inside a rubbish bin that was behind a pile of junk. At the time there were young children around and they don’t hang outside much when the temp is -10. I had the solution contained inside the frame using rubber gloves and tape. It still leaked and needed topping up. It didn’t do a thing, no dissolving. I think it was soaking for around a week. I didn’t want to press my luck any more with the kids around. I’ll have to try it again in the summer, we now live in the bush, no neighbors to worry about. It made a toxic leaky mess.If the mix is right, it won't matter how stuck it is....there's nothing left at the end to take out. It literally desolves to nothing! Its not loosening the post it eats it away from the inside of the post out.
You might have needed a stronger mix. I tried 300ml water to 100g of powder and that just made a light fizz, when it stopped and i tipped it out, nothing much seemed to have desolved.
As i said...its not a first (or even second or third) port of call, but when all else failed, it saved the frame in a very (frame) friendly manner.
Im reasonably good with tools, but the idea of trying to run a reciprocating saw or even a hacksaw blade parallel enough, for a 3 whole cuts down 6" of seatpost is not something i wold greatly enjoy......
Glad you got it out though!